Ophthalmic progressive addition lens for an emmetropic and presbyopic wearer and method of providing same

ABSTRACT

An ophthalmic progressive addition lens for an emmetropic and presbyopic wearer having a mean refractive power, PPO(α, β), a module of resulting astigmatism, ASR(α, β), an acuity loss value ACU(α, β), wherein the (α, β) functions are determined in as-worn conditions of the lens by the wearer, and a first acuity criterion, AcuityCriterion1 which fulfils following requirement: AcuityCriterion1≥435 D 2 .deg 2 , and wherein: AcuityCriterion1 is defined as a combination of PPO(α, β), ASR(α, β), ADD p , and ACU(α, β).

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates generally to the field of vision improvement andmore specifically concerns an ophthalmic progressive addition lens foran emmetropic and presbyopic wearer. It also relates to a method forproviding such a lens.

Discussion of the Background

Conventionally, spectacles lenses are manufactured on request inaccordance with specifications intrinsic to individual wearers. Suchspecifications generally encompass a medical prescription made by anophthalmologist or an eye care practitioner.

An emmetropic wearer has an optical power correction for far visionwhich is near to nil. According to the present invention, one considersthat a emmetropic wearer has a prescribed far vision mean refractivepower which is greater than minus 1 Diopter and less than plus 1Diopter. For presbyopic wearers, the value of the power correction isdifferent for far vision and near vision, due to the difficulties ofaccommodation in near vision. The prescription thus comprises afar-vision power value and an addition representing the power incrementbetween far vision and near vision. The addition is qualified asprescribed addition ADD_(p).

The inventors have noticed that current ophthalmic progressive additionlens for an emmetropic and presbyopic wearer can still be improved so asto enhance the wearer's visual comfort.

A problem that the invention aims to solve is thus to enhance thewearer's visual comfort.

For this purpose, a subject of the invention is an ophthalmicprogressive addition lens for an emmetropic and presbyopic wearer whichhas a prescribed far vision mean refractive power greater than minus 1Diopter and less than plus 1 Diopter and a non nil prescribed addition,ADD_(p), said lens having a mean refractive power, PPO(α, β), a moduleof resulting astigmatism, ASR(α, β), an acuity loss value ACU(α, β),where said (α, β) functions are determined in as-worn conditions of thelens by the wearer, and a first acuity criterion, AcuityCriterion1 whichfulfils following requirement:AcuityCriterion1≥435 D².deg²and where, “D” refers to Diopter, “deg” to degree, AcuityCriterion1 isdefined as a combination of PPO(α, β), ASR(α, β), ADD_(p), and ACU(α,β).

According to an embodiment, AcuityCriterion1 fulfils followingrequirement: AcuityCriterion1≥465 D².deg².

According to an embodiment, AcuityCriterion1 fulfils followingrequirement: AcuityCriterion1≥495 D².deg².

The inventors have discovered that to defining a threshold value of anacuity criterion is suitable to characterize ophthalmic progressiveaddition lens for an emmetropic and presbyopic wearer where the wearer'svisual comfort is enhanced in view of known prior art ophthalmicprogressive addition lens.

SUMMARY OF THE INVENTION

According to different embodiments of the present invention, that may becombined:

-   -   the lens is further characterized by a meridian line, ML(α, β),        a fitting cross, FC(α_(FC), β_(FC)), said (α, β) functions being        determined in as-worn conditions of the lens by the wearer for        gaze directions (α, β) joining the center of rotation of the        eye, CRE, and the lens, where α is a lowering angle in degree        and β is an azimuth angle in degree and wherein:        -   the acuity loss value ACU(α, β) is expressed in logMAR and            defined according to following equation:            ACU(α,β)=−log(AC%(α,β)/100), where:        -   AC %(α, β)=100−63×P(α, β)−44.3×ASR(α, β)+7.2×P(α,            β)²+19.5×P(α, β)×ASR(α, β)+ASR(α, β)²; when P(α, β)≥0; and        -   AC %(α, β)=100−44.3×ASR(α, β)+ASR(α, β)²; when P(α, β)<0;        -   P(α, β)=PPO(α, β)−PPO(α,β_α_mer);        -   β_α_mer is the value of the azimuth angle β on the meridian            line, ML(α, β), at the lowering angle α;    -    and where AcuityCriterion1=Numerator1/Denominator;        -   Numerator1=LAcuSub85(0.1)×LAcuAlpha85(0.1)×ADD_(p) ⁴;        -   Denominator=AsrGradMax×PeaksMean×PVL²;        -   LAcuSub85(0.1) is the angular extent (in deg²) of the zone            where ACU(α, β)≤0.1 logMAR, inside a circle, CIR, centered            on (α, β)=(12,0), which radius is 35 degrees, and where            α≥α85%, α85% being the lowering angle where 85% of the            prescribed addition is perceived by the wearer on the            meridian line;        -   LAcuAlpha85(0.1) is the acuity width (in deg) at α85%            between two iso-acuity loss lines corresponding to 0.1            logMAR and is equal to β₊(ACU(α85%, β)=0.1)−β⁻(ACU(α85%,            β)=0.1), where β₊ is greater than β_α_mer(α85%) and β⁻ is            less than β_α_mer(α85%);        -   PVL is the power variation length is expressed in deg and            defined as being equal to (α85%−α15%), α15% being the            lowering angle where 15% of the prescribed addition is            perceived by the wearer on the meridian line;        -   AsrGradMax is the maximum value of the norm of the gradient            of resulting astigmatism, ASR(α, β), expressed in Diopter            per degree, calculated inside a circle, CIR, centered on (α,            β)=(12,0), which radius is 35 degrees;        -   PeaksMean is the mean maximum module of resulting            astigmatism (in Diopter) which is equal to [ASR_(max)(α_(L),            β_(L))+ASR_(max)(α_(R), β_(R))]/2, where ASR_(max)(α_(L),            β_(L)) is the maximum module of resulting astigmatism on a            side (left side) of the meridian line, and ASR_(max)(α_(R),            β_(R)) is the maximum module of resulting astigmatism on the            other side (right side) of the meridian line that are both            determined inside a circle, CIR, centered on (α, β)=(12,0),            which radius is 35 degrees;    -   a second acuity criterion, AcuityCriterion2, fulfils following        requirement:        AcuityCriterion2≥1110 D².deg², where:        -   AcuityCriterion2=Numerator2/Denominator;        -   Numerator2=LAcuSub85(0.2)×LAcuAlpha85(0.2)×ADD_(p) ⁴;        -   LAcuSub85(0.2) is the angular extent (in deg²) of the zone            where ACU(α, β)≤0.2 logMAR, inside a circle, CIR, centered            on (α, β)=(12,0), which radius is 35 degrees, and where            α≥α85%;        -   LAcuAlpha85(0.2) is the acuity width (in deg) at α85%            between two iso-acuity loss lines corresponding to 0.2            logMAR and is equal to β₊(ACU(α85%, β)=0.2)−β⁻(ACU(α85%,            β)=0.2), where β₊ is greater than β_α_mer(α85%) and β⁻ is            less than β_α_mer(α85%);        -   According to an embodiment, AcuityCriterion2 fulfils            following requirement: AcuityCriterion2≥1130 D².deg².        -   According to an embodiment, AcuityCriterion2 fulfils            following requirement: AcuityCriterion2≥1150 D².deg².    -   a third acuity criterion, AcuityCriterion3, fulfils following        requirement:        AcuityCriterion3≥37.4 D·deg, where:        -   AcuityCriterion3=Numerator3/Denominator;        -   Numerator3=LAcuSubFC(0.1)×ADD_(p) ³;        -   LAcuSubFC(0.1) is the angular extent (in deg²) of the zone            where ACU(α, β)≤0.1 logMAR, inside a circle, CIR, centered            on (α, β)=(12,0), which radius is 35 degrees, and where            α≥α_(FC);        -   According to an embodiment, AcuityCriterion3 fulfils            following requirement: AcuityCriterion3≥37.8 D·deg.        -   According to an embodiment, AcuityCriterion3 fulfils            following requirement: AcuityCriterion3≥38 D·deg.    -   a fourth acuity criterion, AcuityCriterion4, fulfils following        requirement:        AcuityCriterion4≥58.4 D·deg, where:        -   AcuityCriterion4=Numerator4/Denominator;        -   Numerator4=LAcuSubFC(0.2)×ADD_(p) ³;        -   LAcuSubFC(0.2) is the angular extent (in deg²) of the zone            where ACU(α, β)≤0.2 logMAR, inside a circle, CIR, centered            on (α, β)=(12,0), which radius is 35 degrees, and where            α≥α_(FC);        -   According to an embodiment, AcuityCriterion4 fulfils            following requirement: AcuityCriterion4≥59.2 D·deg.        -   According to an embodiment, AcuityCriterion4 fulfils            following requirement: AcuityCriterion4≥60 D·deg.    -   a fifth acuity criterion, AcuityCriterion5, fulfils following        requirement:        AcuityCriterion5≥85 D·deg, where:        -   AcuityCriterion5=Numerator5/Denominator;        -   Numerator5=LAcuDomain(0.1)×ADD_(p) ³;        -   LAcuDomain(0.1) is the angular extent (in deg²) of the zone            where ACU(α, β)≤0.1 logMAR, inside a circle, CIR, centered            on (α, β)=(12,0), which radius is 35 degrees; According to            an embodiment, AcuityCriterion5 fulfils following            requirement: AcuityCriterion5≥85.5 D·deg.        -   According to an embodiment, AcuityCriterion5 fulfils            following requirement: AcuityCriterion5≥86 D·deg.    -   a sixth acuity criterion, AcuityCriterion6, fulfils following        requirement:        AcuityCriterion6≥117.5 D·deg, where:        -   AcuityCriterion6=Numerator6/Denominator;        -   Numerator6=LAcuDomain(0.2)×ADD_(p) ³;        -   LAcuDomain(0.2) is the angular extent (in deg²) of the zone            where ACU(α, β)≤0.2 logMAR, inside a circle, CIR, centered            on (α, β)=(12,0), which radius is 35 degrees.        -   According to an embodiment, AcuityCriterion6 fulfils            following requirement: AcuityCriterion6≥118.3 D·deg.        -   According to an embodiment, AcuityCriterion6 fulfils            following requirement: AcuityCriterion6≥119 D·deg.

In another aspect, the present invention also provides a methodimplemented by computer means for providing an ophthalmic progressiveaddition lens to an emmetropic and presbyopic wearer having a prescribedfar vision mean refractive power greater than minus 1 Diopter and lessthan plus 1 Diopter and a non nil prescribed addition, ADD_(p),comprising the step of calculating a mean refractive power repartition,PPO(α, β), a module of resulting astigmatism repartition, ASR(α, β), anacuity loss value repartition ACU(α, β), where said (α, β) functions arecalculated in as-worn conditions of the lens by the wearer, so as tofulfil following requirement of a first acuity criterion,AcuityCriterion1:AcuityCriterion1≥435 D².deg²;Where, “D” refers to Diopter, “deg” to degree, AcuityCriterion1 isdefined as a combination of PPO(α, β), ASR(α, β), ADD_(p), and ACU(α,β).

According to different embodiments of the method of the presentinvention, that may be combined:

-   -   the method further comprising following steps:        -   Calculating or defining a meridian line, ML(α, β),        -   Calculating or defining a fitting cross, FC(α_(FC), β_(FC)),        -   Calculating the mean refractive power, PPO(α, β), and the            module of resulting astigmatism, ASR(α, β), determined in            as-worn conditions of the lens by the wearer for gaze            directions (α, β) joining the center of rotation of the eye,            CRE, and the lens, where α is a lowering angle in degree and            β is an azimuth angle in degree, an acuity loss value ACU(α,            β) is expressed in logMAR and defined according to following            equation:            ACU(α,β)=−log(AC%(α,β)/100), where:            -   AC %(α, β)=10063×P(α, β)−44.3×ASR(α, β)+7.2×P(α,                β)²+19.5×P(α, β)×ASR(α, β)+ASR(α, β)²; when P(α, β)≥0;                and            -   AC %(α, β)=100−44.3×ASR(α, β)+ASR(α, β)²; when P(α,                β)<0;            -   P(α, β)=PPO(α, β)−PPO(α,β_α_mer);            -   β_α_mer is the value of the azimuth angle β on the                meridian line, ML(α, β), at the lowering angle α;        -   and where AcuityCriterion1=Numerator1/Denominator;            -   Numerator1=LAcuSub85(0.1)×LAcuAlpha85(0.1)×ADD_(p) ⁴;            -   Denominator=AsrGradMax×PeaksMean×PVL²;            -   LAcuSub85(0.1) is the angular extent (in deg²) of the                zone where ACU(α, β)≤0.1 logMAR, inside a circle, CIR,                centered on (α, β)=(12,0), which radius is 35 degrees,                and where α≥α85%, α85% being the lowering angle where                85% of the prescribed addition is perceived by the                wearer on the meridian line;            -   LAcuAlpha85(0.1) is the acuity width (in deg) at α85%                between two iso-acuity loss lines corresponding to 0.1                logMAR and is equal to:                -   β₊(ACU(α85%, β)=0.1)=β⁻(ACU(α85%, β)=0.1), where β₊                    is greater than β_α_mer(α85%) and β⁻ is less than                    β_α_mer(α85%);            -   PVL is the power variation length is expressed in deg                and defined as being equal to (α85%−α15%), α15% being                the lowering angle where 15% of the prescribed addition                is perceived by the wearer on the meridian line;            -   AsrGradMax is the maximum value of the norm of the                gradient of resulting astigmatism, ASR(α, β), expressed                in Diopter per degree, calculated inside a circle, CIR,                centered on (α, β)=(12,0), which radius is 35 degrees;            -   PeaksMean is the mean maximum module of resulting                astigmatism (in Diopter) which is equal to                [ASR_(max)(α_(L), β_(L))+ASR_(max)(α_(R), β_(R))]/2,                where ASR_(max)(α_(L), β_(L)) is the maximum module of                resulting astigmatism on a side (left side) of the                meridian line, and ASR_(max)(α_(R), β_(R)) is the                maximum module of resulting astigmatism on the other                side (right side) of the meridian line that are both                determined inside a circle, CIR, centered on (α,                β)=(12,0), which radius is 35 degrees;    -   one calculates the lens so as to fulfil following requirement of        a second acuity criterion, AcuityCriterion2:        AcuityCriterion2≥1100 D².deg², where:        -   AcuityCriterion2=Numerator2/Denominator;        -   Numerator2=LAcuSub85(0.2)×LAcuAlpha85(0.2)×ADD_(p) ⁴;        -   LAcuSub85(0.2) is the angular extent (in deg²) of the zone            where ACU(α, β)≤0.2 logMAR, inside a circle, CIR, centered            on (α, β)=(12,0), which radius is 35 degrees, and where            α≥α85%;        -   LAcuAlpha85(0.2) is the acuity width (in deg) at α85%            between two iso-acuity loss lines corresponding to 0.2            logMAR and is equal to β₊(ACU(α85%, β)=0.2)−β⁻(ACU(α85%,            β)=0.2), where β₊ is greater than β_α_mer(α85%) and β⁻ is            less than β_α_mer(α85%);    -   one calculates the lens so as to fulfil following requirement of        a third acuity criterion, AcuityCriterion3:        AcuityCriterion3≥37.4 D·deg, where:        -   AcuityCriterion3=Numerator3/Denominator;        -   Numerator3=LAcuSubFC(0.1)×ADD_(p) ³;        -   LAcuSubFC(0.1) is the angular extent (in deg²) of the zone            where ACU(α, β)≤0.1 logMAR, inside a circle, CIR, centered            on (α, β)=(12,0), which radius is 35 degrees, and where            α≥α_(FC);    -   one calculates the lens so as to fulfil following requirement of        a fourth acuity criterion, AcuityCriterion4:        AcuityCriterion4≥58.4 D·deg, where:        -   AcuityCriterion4=Numerator4/Denominator;        -   Numerator4=LAcuSubFC(0.2)×ADD_(p) ³;        -   LAcuSubFC(0.2) is the angular extent (in deg²) of the zone            where ACU(α, β)≤0.2 logMAR, inside a circle, CIR, centered            on (α, β)=(12,0), which radius is 35 degrees, and where            α≥α_(FC);    -   one calculates the lens so as to fulfil following requirement of        a fifth acuity criterion, AcuityCriterion5:        AcuityCriterion5≥85 D·deg, where:        -   AcuityCriterion5=Numerator5/Denominator;        -   Numerator5=LAcuDomain(0.1)×ADD_(p) ³;        -   LAcuDomain(0.1) is the angular extent (in deg²) of the zone            where ACU(α, β)≤0.1 logMAR, inside a circle, CIR, centered            on (α, β)=(12,0), which radius is 35 degrees;    -   one calculates the lens so as to fulfil following requirement of        a sixth acuity criterion, AcuityCriterion6:        AcuityCriterion6≥117.5 D·deg, where:        -   AcuityCriterion6=Numerator6/Denominator;        -   Numerator6=LAcuDomain(0.2)×ADD_(p) ³;        -   LAcuDomain(0.2) is the angular extent (in deg²) of the zone            where ACU(α, β)≤0.2 logMAR, inside a circle, CIR, centered            on (α, β)=(12,0), which radius is 35 degrees;    -   here above requirements of preferred embodiments directed to        AcuityCriterion1 and/or AcuityCriterion2 and/or AcuityCriterion3        and/or AcuityCriterion4 and/or AcuityCriterion5 and/or        AcuityCriterion6 may be chosen within the scope of the method of        the present invention.    -   the method comprises an optimization routine where at least a        target is chosen within requirement of an acuity criterion        chosen in the list consisting of AcuityCriterion1,        AcuityCriterion2, AcuityCriterion3, AcuityCriterion4,        AcuityCriterion5, AcuityCriterion6.

In still another aspect, the present invention relates to a computerprogram product comprising one or more stored sequence of instructionthat is accessible to a processor and which, when executed by theprocessor, causes the processor to carry out at least one of the stepsof the different embodiments of the preceding method.

The invention also relates to a computer-readable medium carrying one ormore sequences of instructions of the preceding computer programproduct.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention, as well as the invention itself,both as to its structure and its operation, will be best understood fromthe accompanying non limiting drawings and examples, taken inconjunction with the accompanying description, in which:

FIGS. 1 and 2 show, diagrammatically, optical systems of eye and lensand ray tracing from the center of rotation of the eye;

FIG. 3 shows field vision zones of an ophthalmic progressive additionlens;

FIGS. 4 to 14 show diagrams helping understanding the definitions of thecriteria used within the frame of the present invention;

FIGS. 15 to 18 give optical characteristics of an ophthalmic progressiveaddition lens according to the prior art;

FIGS. 19 to 22 give optical characteristics of an ophthalmic progressiveaddition lens according to the invention.

On the figures, following references correspond to followings:

-   -   MER is the meridian line;    -   NVGD is the near vision gaze direction;    -   FVGD is the far vision gaze direction;    -   FCGD is the fitting cross gaze direction

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following definitions are provided so as to define the wordings usedwithin the frame of the present invention.

The wordings “wearer's prescription”, also called “prescription data”,are known in the art. Prescription data refers to one or more dataobtained for the wearer and indicating for at least an eye, preferablyfor each eye, a prescribed sphere SPH_(p), and/or a prescribedastigmatism value CYL_(p) and a prescribed axis AXIS_(p) suitable forcorrecting the ametropia of each eye for the wearer and, if suitable, aprescribed addition ADD_(p) suitable for correcting the presbyopia ofeach of his eyes.

“Progressive ophthalmic addition lenses” are known in the art. Accordingto the invention, the lens may be a standard lens but also a lens forinformation glasses, wherein the lens comprises means for displayinginformation in front of the eye. The lens may also be suitable forsunglasses or not. All ophthalmic lenses of the invention may be pairedso as to form a pair of lenses (left eye LE, right eye RE).

A “gaze direction” is identified by a couple of angle values (α,β),wherein said angles values are measured with regard to reference axescentered on the center of rotation of the eye, commonly named as “CRE”.More precisely, FIG. 1 represents a perspective view of such a systemillustrating parameters α and β used to define a gaze direction. FIG. 2is a view in the vertical plane parallel to the antero-posterior axis ofthe wearer's head and passing through the center of rotation of the eyein the case when the parameter β is equal to 0. The center of rotationof the eye is labeled CRE. The axis CRE-F′, shown on FIG. 2 in adot-dash line, is the horizontal axis passing through the center ofrotation of the eye and extending in front of the wearer that is theaxis CRE-F′ corresponding to the primary gaze direction. The lens isplaced and centered in front of the eye such that the axis CRE-F′ cutsthe front surface of the lens on a point called the fitting cross, whichis, in general, present on lenses to enable the positioning of lenses ina frame by an optician. The point of intersection of the rear surface ofthe lens and the axis CRE-F′ is the point, O. A vertex sphere, whichcenter is the center of rotation of the eye, CRE, and has a radiusq′=O−CRE, intercepts the rear surface of the lens in a point of thehorizontal axis. A value of radius q′ of 25.5 mm corresponds to a usualvalue and provides satisfying results when wearing the lenses. Othervalue of radius q′ may be chosen. A given gaze direction, represented bya solid line on FIG. 1, corresponds to a position of the eye in rotationaround CRE and to a point J (see FIG. 2) of the vertex sphere; the angleβ is the angle formed between the axis CRE-F′ and the projection of thestraight line CRE-J on the horizontal plane comprising the axis CRE-F′;this angle appears on the scheme on FIG. 1. The angle α is the angleformed between the axis CRE-J and the projection of the straight lineCRE-J on the horizontal plane comprising the axis CRE-F′; this angleappears on the scheme on FIGS. 1 and 2. A given gaze view thuscorresponds to a point J of the vertex sphere or to a couple (α,β). Themore the value of the lowering gaze angle is positive, the more the gazeis lowering and the more the value is negative, the more the gaze isrising. In a given gaze direction, the image of a point M in the objectspace, located at a given object distance, is formed between two pointsS and T corresponding to minimum and maximum distances JS and JT, whichwould be the sagittal and tangential local focal lengths. The image of apoint in the object space at infinity is formed, at the point F′. Thedistance D corresponds to the rear frontal plane of the lens.

For each gaze direction (α,β), a mean refractive power PPO(α,β), amodule of astigmatism ASR(α,β) and an axis AXE(α,β) of this astigmatism,and a module of resulting (also called residual or unwanted) astigmatismASR(α,β) are defined.

“Astigmatism” refers to astigmatism generated by the lens, or toresidual astigmatism (resulting astigmatism) which corresponds to thedifference between the prescribed astigmatism (wearer astigmatism) andthe lens-generated astigmatism; in each case, with regards to amplitudeor both amplitude and axis;

“Ergorama” is a function associating to each gaze direction the usualdistance of an object point. Typically, in far vision following theprimary gaze direction, the object point is at infinity. In near vision,following a gaze direction essentially corresponding to an angle α ofthe order of 35° and to an angle β of the order of 5° in absolute valuetowards the nasal side, the object distance is of the order of 30 to 50cm. For more details concerning a possible definition of an ergorama,U.S. Pat. No. 6,318,859 may be considered. This document describes anergorama, its definition and its modeling method. For a method of theinvention, points may be at infinity or not. Ergorama may be a functionof the wearer's ametropia. Using these elements, it is possible todefine a wearer optical power and astigmatism, in each gaze direction.An object point M at an object distance given by the ergorama isconsidered for a gaze direction (α,β). An object proximity ProxO isdefined for the point M on the corresponding light ray in the objectspace as the inverse of the distance MJ between point M and point J ofthe vertex sphere:ProxO=1/MJThis enables to calculate the object proximity within a thin lensapproximation for all points of the vertex sphere, which is used for thedetermination of the ergorama. For a real lens, the object proximity canbe considered as the inverse of the distance between the object pointand the front surface of the lens, on the corresponding light ray.For the same gaze direction (α,β), the image of a point M having a givenobject proximity is formed between two points S and T which correspondrespectively to minimal and maximal focal distances (which would besagittal and tangential focal distances). The quantity ProxI is calledimage proximity of the point M:

${\Pr\;{oxI}} = {\frac{1}{2}\left( {\frac{1}{JT} + \frac{1}{JS}} \right)}$By analogy with the case of a thin lens, it can therefore be defined,for a given gaze direction and for a given object proximity, i.e. for apoint of the object space on the corresponding light ray, an opticalpower PPO as the sum of the image proximity and the object proximity.PPO=ProxO+ProxIThe optical power is also called refractive power.With the same notations, an astigmatism AST is defined for every gazedirection and for a given object proximity as:

${AST} = {{\frac{1}{JT} - \frac{1}{JS}}}$This definition corresponds to the astigmatism of a ray beam created bythe lens. The resulting astigmatism ASR is defined for every gazedirection through the lens as the difference between the actualastigmatism value AST for this gaze direction and the prescribedastigmatism for the same lens. The residual astigmatism (resultingastigmatism) ASR more precisely corresponds to module of the vectorialdifference between actual (AST, AXE) and prescription data (CYL_(p),AXIS_(p)).

When the characterization of the lens is of optical kind, it refers tothe ergorama-eye-lens system described above. For simplicity, the term‘lens’ is used in the description but it has to be understood as the‘ergorama-eye-lens system’. The values in optic terms can be expressedfor gaze directions. Conditions suitable to determine of theergorama-eye-lens system are called in the frame present invention“as-worn conditions”.

In the remainder of the description, terms like «up», «bottom»,«horizontal», «vertical», «above», «below», or other words indicatingrelative position may be used. These terms are to be understood in thewearing conditions of the lens. Notably, the “upper” part of the lenscorresponds to a negative lowering angle α<0° and the “lower” part ofthe lens corresponds to a positive lowering angle α>0°.

A “far-vision gaze direction”, referred as FVGD, is defined for a lens,as the vision gaze direction corresponding to the far vision (distant)reference point and thus (α_(FV), β_(FV)), where the mean refractivepower is substantially equal to the mean prescribed power in far vision,the mean prescribed power being equal to SPH_(p)+(CYL_(p)/2). Within thepresent disclosure, far-vision is also referred to as distant-vision.

A “near-vision gaze direction”, referred as NVGD, is defined for a lens,as the vision gaze direction corresponding to the near vision (reading)reference point, and thus (α_(NV), β_(NV)), where the refractive poweris substantially equal to the prescribed power in far vision plus theprescribed addition, ADD_(p).

A “fitting-cross gaze direction”, referred as FCGD, is defined for alens, as the vision gaze direction corresponding to the fitting crossreference point and thus (α_(FC), β_(FC)).

The “meridian line”, referred as ML(α,β), of a progressive lens is aline defined from top to bottom of the lens and passing through thefitting cross where one can see clearly an object point. Said meridianline is defined on the basis of the repartition of module of resultingastigmatism, ASR, over the (α, β) domain and substantially correspond tothe center of the two central iso-module of resulting astigmatism valueswhich value is equal to 0.25 Diopter. To be more specific and accordingto the present invention the meridian line is calculated according tofollowing method:

-   -   One defines the gaze direction, FCGD, corresponding to the        fitting cross (α_(FC), β_(FC));    -   One calculates the lowering angle α_(NV) corresponding to the        near vision gaze direction;    -   For each lowering angle α comprised between α_(FC) and α_(NV),        one calculates the azimuth angle β corresponding to the midway        direction between the two central iso-module of resulting        astigmatism values which value is equal to 0.25 Diopter; said        calculated directions are referred as (α_(i), β_(i)); one        calculates a straight line, d2, so as to minimizes the deviation        of (α_(i), β_(i)) to said straight line, according to following        equation:

d 2 : β(α) = a₂α + b₂; α_(FC) < α < α_(NV)$a_{2},{b_{2}:{\min\left\{ {\sum\limits_{i}\left( {{a_{2}\alpha_{i}} + b_{2} - \beta_{i}} \right)^{2}} \right\}}}$

-   -    where «min» function relates to determining the a₂ and b₂        parameters so as to minimize the equation between brackets.        -   One calculates a pivot direction (α_(piv), β_(piv)) defined            as the intersection between the straight line d2 and a line            corresponding to β=β_(FC), where

$:\left\{ \begin{matrix}{\alpha_{PIV} = \frac{\left( {\beta_{FC} - b_{2}} \right)}{a_{2}}} \\{\beta_{PIV} = \beta_{FC}}\end{matrix} \right.$

-   -   One calculates a straight line, d1, where: d1: β(α)=β_(piv);        α<α_(piv);    -   One determines β_(NV) as being the azimuth angle β of straight        line d2 for α_(NV); where: β_(NV)=a₂α_(NV)+b₂;    -   For each lowering angle α greater than α_(NV), one determines        the azimuth angle β corresponding to the midway direction        between the two central iso-module of resulting astigmatism        values which value is equal to 0.25 Diopter; said calculated        directions are referred as (α_(j), β_(j)); one calculates a        straight line, d3, so as to minimizes the deviation of (α_(j),        β_(j)) to said straight line and that passes at the direction        (α_(NV), β_(NV)); if the calculated slope is negative, the        sloped is chosen to be nil; d3 is thus defined according to        following equation:

${{{{d\; 3}:{\beta(\alpha)}} = {{a_{3}\left( {\alpha - \alpha_{NV}} \right)} + \beta_{NV}}};{\alpha_{NV} < {\alpha a_{3}}}},{:{\min\left\{ {{\sum\limits_{j}\left( {{a_{3}\left( {\alpha_{j} - \alpha_{NV}} \right)} + \beta_{NV} - \beta_{j}} \right)^{2}};{a_{3} \geq 0}} \right\}}}$

-   -   The meridian line is finally defined as being the line built        when following the three segments d1, d2, d3.

“Micro-markings” also called “alignment reference marking” have beenmade mandatory on progressive lenses by the harmonized standards ISO13666:2012 (“Alignment reference marking: permanent markings provided bythe manufacturer to establish the horizontal alignment of the lens orlens blank, or to re-establish other reference points”) and ISO 8990-2(“Permanent marking: the lens has to provide at least followingpermanent markings: alignment reference markings comprising two markingsdistant from 34 mm one of each other, equidistant from a vertical planepassing through the fitting cross or the prism reference point”).Micro-markings that are defined the same way are also usually made oncomplex surfaces, such as on a front surface of a lens with a frontsurface comprising a progressive or regressive front surface.

“Temporary markings” may also be applied on at least one of the twosurfaces of the lens, indicating positions of control points (referencepoints) on the lens, such as a control point for far-vision, a controlpoint for near-vision, a prism reference point and a fitting cross forinstance. The prism reference point PRP is considered here at themidpoint of the straight segment which connects the micro-markings. Ifthe temporary markings are absent or have been erased, it is alwayspossible for a skilled person to position the control points on the lensby using a mounting chart and the permanent micro-markings. Similarly,on a semi-finished lens blank, standard ISO 10322-2 requiresmicro-markings to be applied. The centre of the aspherical surface of asemi-finished lens blank can therefore be determined as well as areferential as described above.

FIG. 3 shows field vision zones of an ophthalmic progressive additionlens 30 where said lens comprises a far vision (distant vision) zone 32located in the upper part of the lens, a near vision zone 36 located inthe lower part of the lens and an intermediate zone 34 situated betweenthe far vision zone 32 and the near vision zone 36. The meridian line isreferred as 38.

A plurality of criteria has been defined in the scope of the presentinvention and there definitions are illustrated by FIGS. 4 to 13.

In the background of FIGS. 4 to 11, the acuity loss contour plot of asame example of an ophthalmic progressive addition lens is represented.

In the background of FIG. 12, the module of resulting astigmatismcontour plot of the same example of an ophthalmic progressive additionlens is represented.

In the background of FIG. 13, the norm of the gradient of resultingastigmatism contour plot of the same example of an ophthalmicprogressive addition lens is represented.

The acuity loss contour shows the variations over the (α, β) domain ofthe acuity loss value ACU(α, β); the acuity loss value is expressed inlogMAR.

The acuity loss value ACU(α, β) is defined according to followingequation:ACU(α,β)=−log(AC%(α,β)/100);AC %(α, β) is an acuity function defined as a function of both meanrefractive power, PPO(α, β), and module of resulting astigmatism, ASR(α,β); where:

-   -   one defines a mean refractive power difference function, P(α,        β), where:        P(α,β)=PPO(α,β)−PPO(α,β_α_mer);    -    β_α_mer being the value of the azimuth angle β on the meridian        line, ML(α, β), at the lowering angle α;    -   if P(α, β)≥0, AC %(α, β) is defined according to following        equation:        AC%(α,β)={100−63×P(α,β)−44.3×ASR(α,β)+7.2×P(α,β)²+19.5×P(α,β)×ASR(α,β)+ASR(α,β)²}    -   if P(α, β)<0, AC %(α, β) is defined according to following        equation:        AC%(α,β)=100−44.3×ASR(α,β)+ASR(α,β)².

Bibliographical reference of such an acuity loss definition can be foundin following document: Fauquier, C., et al. “Influence of combined powererror and astigmatism on visual acuity.” Vision Science and ItsApplications, OSA Technical Digest Series. Washington, D.C.: OpticalSociety of America (1995): 151-4.

Acuity loss values ACU(α, β) of the example lens are plotted in thebackground of FIGS. 4 to 11 and curves indicates iso-acuity loss valueswhere there is an increment of 0.1 logMAR between neighbouring curves ofdifferent acuity loss values. On all these figures, a circle, referredas CIR, is represented; said circle is centered on (α, β)=(12,0) and itsradius is equal to 35 degree. Said circle represent the angular zonewithin which the criteria of the invention are defined.

FIG. 4 shows how to calculate criterion LAcuSub85(0.1); LAcuSub85(0.1)is the angular extent (in deg²) of the zone (in grey on the figure)between the two central neighbouring curves of acuity loss equal to 0.1logMAR, said angular extent being calculated inside the circle CIR, andfor lowering angle α more than α85% (i.e. for α≥α85%), where α85% isdefined as the lowering angle where 85% of the prescribed addition isperceived by the wearer on the meridian line. The lowering angle of themeridian line where 85% of the prescribed addition is perceived by thewearer is defined in the frame of the present invention as being theangle lowering α where the mean refractive power, PPO(α85%), fulfillsfollowing equation:PPO(α85%)=PPO(FVGD)+0.85×ADD_(p),and where PPO(FVGD) is the mean refractive power according to thefar-vision gaze direction, FVGD.

Similar definition is used for “a lowering angle of the meridian linewhere 15% of the prescribed addition is perceived by the wearer” whichcorresponds to the lowering angle α where the mean refractive power,PPO(α15%), fulfills following equation:PPO(α15%)=PPO(FVGD)+0.15×ADD_(p).

FIG. 5 shows how to calculate criterion LAcuSub85(0.2); LAcuSub85(0.2)is the angular extent (in deg²) of the zone (in grey on the figure)between the two central neighbouring curves of acuity loss equal to 0.2logMAR, said angular extent being calculated inside the circle CIR, andfor lowering angle α more than α85% (i.e. for α≥α85%).

FIG. 6 shows how to calculate criterion LAcuAlpha85(0.1);LAcuAlpha85(0.1) is the acuity width (in deg) at α85% between the twocentral neighbouring curves of acuity loss equal to 0.1 logMAR; it isequal to β+(ACU(α85%, β)=0.1)−β−(ACU(α85%, β)=0.1), where β+ is greaterthan β_α_mer(α85%) and β− is less than β_α_mer(α85%).

FIG. 7 shows how to calculate criterion LAcuAlpha85(0.2);LAcuAlpha85(0.2) is the acuity width (in deg) at α85% between the twocentral neighbouring curves of acuity loss equal to 0.2 logMAR; it isequal to β+(ACU(α85%, β)=0.2)−β−(ACU(α85%, β)=0.2), where β+ is greaterthan β_α_mer(α85%) and β− is less than β_α_mer(α85%).

FIG. 8 shows how to calculate criterion LAcuSubFC(0.1); LAcuSubFC(0.1)is the angular extent (in deg²) of the zone (in grey on the figure)between the two central neighbouring curves of acuity loss equal to 0.1logMAR, said angular extent being calculated inside the circle CIR, andfor a more than α_(FC) (i.e. for α≥α_(FC)).

FIG. 9 shows how to calculate criterion LAcuSubFC(0.2); LAcuSubFC(0.2)is the angular extent (in deg²) of the zone (in grey on the figure)between the two central neighbouring curves of acuity loss equal to 0.2logMAR, said angular extent being calculated inside the circle CIR, andfor a more than α_(FC) (i.e. for α≥α_(FC)).

FIG. 10 shows how to calculate criterion LAcuDomain(0.1);LAcuDomain(0.1) is the angular extent (in deg²) of the zone (in grey onthe figure) between the two central neighbouring curves of acuity lossequal to 0.1 logMAR, said angular extent being calculated inside thewhole circle CIR.

FIG. 11 shows how to calculate criterion LAcuDomain(0.2);LAcuDomain(0.2) is the angular extent (in deg²) of the zone (in grey onthe figure) between the two central neighbouring curves of acuity lossequal to 0.2 logMAR, said angular extent being calculated inside thewhole circle CIR.

FIG. 12 shows how to calculate criterion PeaksMean; the module ofresulting astigmatism values of the example lens are plotted in thebackground of FIG. 12 and curves indicates iso-module of resultingastigmatism values where there is an increment of 0.25 Diopter betweenneighbouring curves of different module of resulting astigmatism values.Previously defined Circle, CIR, is represented; PeaksMean is the meanmaximum module of resulting astigmatism (in Diopter) which is equal to[ASR_(max)(α_(L), β_(L))+ASR_(max)(α_(R), β_(R))]/2, whereASR_(max)(α_(L), β_(L)) is the maximum module of resulting astigmatismon a side (left side) of the meridian line, and ASR_(max)(α_(R), β_(R))is the maximum module of resulting astigmatism on the other side (rightside) of the meridian line that are both determined inside the circle,CIR.

FIG. 13 shows how to calculate criterion AsrGradMax; the norm of thegradient of resulting astigmatism values of the example lens are plottedin the background of FIG. 13 and curves indicates iso-norm of thegradient of resulting astigmatism values where there is an increment of0.05 Diopter between neighbouring curves of different norm of thegradient of resulting astigmatism values. AsrGradMax is defined as themaximum value of the norm of the gradient of resulting astigmatism,ASR(α, β), expressed in Diopter per degree, calculated inside thecircle, CIR. The zone where said maximum value of the norm of thegradient of resulting astigmatism appears on FIG. 13 is indicated as asmall circle for a about +15 degree.

Gradient of resulting astigmatism is a vector V which components arefollowing:

$V_{\alpha} = \frac{\partial{ASR}}{\partial\alpha}$$V_{\beta} = \frac{\partial{ASR}}{\partial\beta}$Its norm is given by following equation:∥V∥=√{square root over (V _(α) ² +V _(β) ²)}According to an example, one determinates the gradient of resultingastigmatism using a finite difference method;According to an example:

$V_{\alpha} \approx \frac{{{ASR}\left( {{\alpha + ɛ},\beta} \right)} - {{ASR}\left( {{\alpha - ɛ},\beta} \right)}}{2ɛ}$$V_{\beta} \approx \frac{{{ASR}\left( {\alpha,{\beta + ɛ}} \right)} - {{ASR}\left( {\alpha,{\beta - ɛ}} \right)}}{2ɛ}$According to an example, ε=0.1 deg.Circle, referred as CIR, and centered on (α, β)=(12,0) with a radius isequal to 35 degree is called “Domain”. AsrGradMax can be definedaccording to following equation:AsrGradMax=Max{∥V(α,β)∥;(α,β)∈Domain}

FIG. 14 shows the variation of object proximity ProxO as a function ofthe lowering angle α used to define the ergorama in view of U.S. Pat.No. 6,318,859.

The ergorama used in the frame of the present invention is definedthanks to following data, where object proximity values are given forlowering angles α:

Alpha ProxO [deg] [D] −50 0 −40 0 −30 0 −20 0 −10 0 0 0 10 1.65 20 2.5430 2.78 40 2.93 50 2.98

EXAMPLES

FIGS. 15 to 18 give optical characteristics of an ophthalmic progressiveaddition lens according to the prior art, hereafter referred as“PA_lens”.

FIGS. 19 to 22 give optical characteristics of an ophthalmic progressiveaddition lens according to the invention, hereafter referred as“INV_lens”.

Said both ophthalmic progressive addition lenses have been designed soas to fulfil following prescribed features:

-   -   prescribed sphere SPH_(p)=0 Diopter    -   prescribed astigmatism value CYL_(p)=0 Diopter    -   prescribed axis AXIS_(p)=0°    -   prescribed addition ADD_(p)=2 Diopter

FIGS. 15 and 19 represent the mean refractive power repartition profile,PPO, as a function of the lowering angle α, along the meridian line, forrespectively the prior art ophthalmic progressive addition lens and theophthalmic progressive addition lens according to the present invention.Lowering angles corresponding to α85% and to α15% are indicated.

FIGS. 16 and 20 represent the mean refractive power repartition, PPO,over the (α, β) domain, for respectively the prior art ophthalmicprogressive addition lens and the ophthalmic progressive addition lensaccording to the present invention. Curves indicates iso-mean refractivepower values where there is an increment of 0.25 Diopter betweenneighbouring curves of different module of resulting astigmatism values.

FIGS. 17 and 21 represent respectively the module of resultingastigmatism repartition, ASR, over the (α, β) domain, for respectivelythe prior art ophthalmic progressive addition lens and the ophthalmicprogressive addition lens according to the present invention. Curvesindicates iso-module of resulting astigmatism values where there is anincrement of 0.25 Diopter between neighbouring curves of differentmodule of resulting astigmatism values.

FIGS. 18 and 22 represent respectively the acuity loss value repartitionACU, over the (α, β) domain, for respectively the prior art ophthalmicprogressive addition lens and the ophthalmic progressive addition lensaccording to the present invention. Curves indicates iso-acuity lossvalues where there is an increment of 0.1 logMAR between neighbouringcurves of different module of resulting astigmatism values.

Here above defined acuity criteria have been calculated for the saidboth ophthalmic progressive addition lenses. Results are reported herebellow.

Lens PA_lens INV_lens AcuityCriterion1 431 520 AcuityCriterion2 10151190 AcuityCriterion3 37 40 AcuityCriterion4 58 61 AcuityCriterion5 8490 AcuityCriterion6 117 122

The inventors have done tests that demonstrate that the chosen thresholdvalue of AcuityCriterion1, and optionally the chosen threshold values ofAcuityCriterion2 and/or AcuityCriterion3 and/or AcuityCriterion4 and/orAcuityCriterion5 and/or AcuityCriterion6, is (are) suitable forproviding to an emmetropic and presbyopic wearer an ophthalmicprogressive addition lens where the wearer's visual comfort is enhancedin view of known prior art ophthalmic progressive addition lens.

The invention claimed is:
 1. An ophthalmic progressive addition lens foran emmetropic and presbyopic wearer which has a prescribed far visionmean refractive power greater than minus 1 Diopter and less than plus 1Diopter and a non nil prescribed addition, ADD_(p), said lens having amean refractive power, PPO(α, β), a module of resulting astigmatism,ASR(α, β), an acuity loss value ACU(α, β), where said (α, β) functionsare determined in as-worn conditions of the lens by the wearer, and afirst acuity criterion, AcuityCriterion1 which fulfils followingrequirement:AcuityCriterion1≥435 D².deg², and where: “D” refers to Diopter, “deg” todegree, AcuityCriterion1 is defined as a combination of PPO(α, β),ASR(α, β), ADD_(P), and ACU(α, β), wherein the lens is furthercharacterized by a meridian line, ML(α, β), a fitting cross, FC(α_(FC),β_(FC)), said (α, β) functions being determined in as-worn conditions ofthe lens by the wearer for gaze directions (α, β) joining the center ofrotation of the eye, CRE, and the lens, where α is a lowering angle indegree and β is an azimuth angle in degree and wherein: the acuity lossvalue ACU(α, β) is expressed in logMAR and defined according tofollowing equation:ACU(α,β)=−log(AC %(α,β)/100), where: AC %(α, β)=100−63×P(α,β)−44.3×ASR(α, β)+7.2×P(α, β)²+19.5×P(α, β)×ASR(α, β)+ASR(α, β)²; whenP(α, β)≥0; and AC %(α, β)=100−44.3×ASR(α, β)+ASR(α, β)²; when P(α, β)<0;P(α, β)=PPO(α, β)−PPO(α, β_α_mer); β_α_mer is the value of the azimuthangle β on the meridian line, ML(α, β), at the lowering angle α; andwhere AcuityCriterion1=Numerator1/Denominator:Numerator1=LAcuSub85(0.1)×LAcuAlpha85(0.1)×ADD_(p) ⁴;Denominator=AsrGradMax×PeaksMean×PVL²; LAcuSub85(0.1) is the angularextent (in deg²) of the zone where ACU(α, β)≤0.1 logMAR, inside acircle, CIR, centered on (α, β)=(12,0), which radius is 35 degrees, andwhere α≥α85%, α85% being the lowering angle where 85% of the prescribedaddition is perceived by the wearer on the meridian line;LAcuAlpha85(0.1) is the acuity width (in deg) at α85% between twoiso-acuity loss lines corresponding to 0.1 logMAR and is equal toβ₊(ACU(α85%, β)=0.1)−β⁻(ACU(α85%, β)=0.1), where β₊ is greater thanβ_α_mer(α85%) and β⁻ is less than β_α_mer(α85%); PVL is the powervariation length is expressed in deg and defined as being equal to(α85%−α15%), α15% being the lowering angle where 15% of the prescribedaddition is perceived by the wearer on the meridian line; AsrGradMax isthe maximum value of the norm of the gradient of resulting astigmatismASR(α, β), expressed in Diopter per degree, calculated inside a circle,CIR, centered on (α, β)=(12,0), which radius is 35 degrees; PeaksMean isthe mean maximum module of resulting astigmatism (in Diopter,) which isequal to [ASR_(max)(α_(L), β_(L))+ASR_(max)(α_(R), β_(R))]/2, whereASR_(max)(α_(L), β_(L)) is the maximum module of resulting astigmatismon a side (left side) of the meridian line, and ASR_(max)(α_(R), β_(R))is the maximum module of resulting astigmatism on the other side (rightside) of the meridian line that are both determined inside a circle,CIR, centered on (α, β)=(12,0), which radius is 35 degrees.
 2. Anophthalmic progressive addition lens as claimed in claim 1, according towhich a second acuity criterion, AcuityCriterion2, fulfils followingrequirement:AcuityCriterion2≥1100 D².deg², where:AcuityCriterion2=Numerator2/Denominator;Numerator2=LAcuSub85(0.2)×LAcuAlpha85(0.2)×ADD_(p) ⁴; LAcuSub85(0.2) isthe angular extent (in deg²) of the zone where ACU(α, β)≤0.2 logMAR,inside a circle, CIR, centered on (α, β)=(12,0), which radius is 35degrees, and where α≥α85%; LAcuAlpha85(0.2) is the acuity width (in deg)at α85% between two iso-acuity loss lines corresponding to 0.2 logMARand is equal to β₊(ACU(α85%, β)=0.2)−β⁻(ACU(α85%, β)=0.2), where β₊ isgreater than β_α_mer(α85%) and β⁻ is less than β_α_mer(α85%).
 3. Anophthalmic progressive addition lens as claimed in claim 1, according towhich a third acuity criterion, AcuityCriterion3, fulfils followingrequirement:AcuityCriterion3≥37.4 D·deg, where:AcuityCriterion3=Numerator3/Denominator;Numerator3=LAcuSubFC(0.1)×ADD_(p) ³; LAcuSubFC(0.1) is the angularextent (in deg²) of the zone where ACU(α, β)≤0.1 logMAR, inside acircle, CIR, centered on (α, β)=(12,0), which radius is 35 degrees, andwhere α≥aα_(FC).
 4. An ophthalmic progressive addition lens as claimedin claim 1, according to which a fourth acuity criterion,AcuityCriterion4, fulfils following requirement:AcuityCriterion4≥58.4 D·deg, where:AcuityCriterion4=Numerator4/Denominator;Numerator4=LAcuSubFC(0.2)×ADD_(D) ³; LAcuSubFC(0.2) is the angularextent (in deg²) of the zone where ACU(α, β)≤0.2 logMAR, inside acircle, CIR, centered on (α, β)=(12,0), which radius is 35 degrees, andwhere α≥α_(FC).
 5. An ophthalmic progressive addition lens as claimed inclaim 1, according to which a fifth acuity criterion, AcuityCriterion5,fulfils following requirement:AcuityCriterion5≥85 D·deg, where:AcuityCriterion5=Numerator5/Denominator;Numerator5=LAcuDomain(0.1)×ADD_(p) ³; LAcuDomain(0.1) is the angularextent (in deg²) of the zone where ACU(α, β) 0.1 logMAR, inside acircle, CIR, centered on (α, β)=(12,0), which radius is 35 degrees. 6.An ophthalmic progressive addition lens as claimed in claim 1, accordingto which a sixth acuity criterion, AcuityCriterion6, fulfils followingrequirement:AcuityCriterion6≥117.5 D·deg, where:AcuityCriterion6=Numerator6/Denominator;Numerator6=LAcuDomain(0.2)×ADD_(p) ³; LAcuDomain(0.2) is the angularextent (in deg) of the zone where ACU(α, β)≤0.2 logMAR, inside a circle,CIR, centered on (α, β)=(12,0), which radius is 35 degrees.
 7. A methodimplemented by computer means for providing an ophthalmic progressiveaddition lens to an emmetropic and presbyopic wearer having a prescribedfar vision mean refractive power greater than minus 1 Diopter and lessthan plus 1 Diopter and a non nil prescribed addition, ADD_(p),comprising the step of calculating a mean refractive power repartition,PPO(α, β), a module of resulting astigmatism repartition, ASR(α, β), anacuity loss value repartition ACU(α, β), where said (α, β) functions arecalculated in as-worn conditions of the lens by the wearer, so as tofulfil following requirement of a first acuity criterion,AcuityCriterion1:AcuityCriterion1≥435 D².deg²; “D” refers to Diopter, “deg” to degree,AcuityCriterion1 is defined as a combination of PPO(α, β), ASR(α, β),ADD_(p), and ACU(α, β), wherein the method further comprising thefollowing steps: calculating or defining a meridian line, ML(α, β),calculating or defining a fitting cross, FC(α_(FC), β_(FC)), calculatingthe mean refractive power, PPO(α, β), and the module of resultingastigmatism, ASR(α, β), determined in as-worn conditions of the lens bythe wearer for gaze directions (α, β) joining the center of rotation ofthe eye, CRE, and the lens, where α is a lowering angle in degree and βis an azimuth angle in degree, an acuity loss value ACU(α, β) isexpressed in logMAR and defined according to following equation:ACU(α,β)=−log(AC %(α,β)/100), where: AC %(α, β)=100−63×P(α,β)−44.3×ASR(α, β)+7.2×P(α, β)²+19.5×P(α, β)×ASR(α, β)+ASR(α, β)²; whenP(α, β)≥0; and AC %(α, β)=100−44.3×ASR(α, β)+ASR(α, β)²; when P(α, β)<0;P(α, β)=PPO(α, β)−PPO(α, β_α_mer): β_α_mer is the value of the azimuthangle β on the meridian line, ML(α, β), at the lowering angle α; andwhere AcuitvCriterionl=Numerator1/Denominator:Numerator1=LAcuSub85(0.1)×LAcuAlpha85(0.1)×ADD_(p) ⁴;Denominator=AsrGradMax×PeaksMean×PVL²; LAcuSub85(0.1) is the angularextent (in deg²) of the zone where ACU(α, β)≤0.1 logMAR, inside acircle, CIR, centered on (α, β)=(12,0), which radius is 35 degrees, andwhere α≥α85%, α85% being the lowering angle where 85% of the prescribedaddition is perceived by the wearer on the meridian line;LAcuAlpha85(0.1) is the acuity width (in deg) at α85% between twoiso-acuity loss lines corresponding to 0.1 logMAR and is equal to:β₊(ACU(α85%, β)=0.1)−β⁻(ACU(α85%, β)=0.1), where β₊ is greater thanβ_α_mer(α85%) and β⁻ is less than β_α_mer(α85%); PVL is the powervariation length is expressed in deg and defined as being equal to(α85%−α15%), α15% being the lowering angle where 15% of the prescribedaddition is perceived by the wearer on the meridian line; AsrGradMax isthe maximum value of the norm of the gradient of resulting astigmatism,ASR(α, β), expressed in Diopter per degree, calculated inside a circle,CIR, centered on (α, β)=(12,0), which radius is 35 degrees; PeaksMean isthe mean maximum module of resulting astigmatism (in Diopter) which isequal to [ASR_(max)(α_(L), β_(L))+ASR_(max)(α_(R), β_(R))]/2, whereASR_(max)(α_(L), β_(L)) is the maximum module of resulting astigmatismon a side (left side) of the meridian line, and ASR_(max)(α_(R), β_(R))is the maximum module of resulting astigmatism on the other side (rightside) of the meridian line that are both determined inside a circle,CIR, centered on (α, β)=(12,0), which radius is 35 degrees.
 8. Themethod for providing an ophthalmic progressive addition lens as claimedin claim 7, according to which one calculates the lens so as to fulfilfollowing requirement of a second acuity criterion, AcuityCriterion2:AcuityCriterion2≥1100 D².deg², where:AcuityCriterion2=Numerator2/Denominator;Numerator2=LAcuSub85(0.2)×LAcuAlpha85(0.2)×ADD_(p) ⁴; LAcuSub85(0.2) isthe angular extent (in deg²) of the zone where ACU(α, β)≤0.2 logMAR,inside a circle, CIR, centered on (α, β)=(12,0), which radius is 35degrees, and where α≥α85%; LAcuAlpha85(0.2) is the acuity width (in deg)at α85% between two iso-acuity loss lines corresponding to 0.2 logMARand is equal to β₊(ACU(α85%, β)=0.2)−β⁻(ACU(α85%, β)=0.2), where β₊isgreater than β_α_mer(α85%) and β⁻ is less than β_α_mer(α85%).
 9. Themethod for providing an ophthalmic progressive addition lens as claimedin claim 7, according to which one calculates the lens so as to fulfilfollowing requirement of a third acuity criterion, AcuityCriterion3:AcuityCriterion3≥37.4 D.deg, where:AcuityCriterion3=Numerator3/Denominator;Numerator3=LAcuSubFC(0.1)×ADD_(p) ³; LAcuSubFC(0.1) is the angularextent (in deg²) of the zone where ACU(α, β)≤0.1 logMAR, inside acircle, CIR, centered on (α, β)=(12,0), which radius is 35 degrees, andwhere α≥α_(FC).
 10. The method for providing an ophthalmic progressiveaddition lens as claimed in claim 7, according to which one calculatesthe lens so as to fulfil following requirement of a fourth acuitycriterion, AcuityCriterion4:AcuityCriterion4≥58.4 D.deg, where:AcuityCriterion4=Numerator4/Denominator;Numerator4=LAcuSubFC(0.2)×ADD_(p) ³; LAcuSubFC(0.2) is the angularextent (in deg²) of the zone where ACU(α, β)≤0.2 logMAR, inside acircle, CIR, centered on (α, β)=(12,0), which radius is 35 degrees, andwhere α≥α_(FC).
 11. The method for providing an ophthalmic progressiveaddition lens as claimed in claim 7, according to which one calculatesthe lens so as to fulfil following requirement of a fifth acuitycriterion, AcuityCriterion5:AcuityCriterion5≥85 D.deg, where:AcuityCriterion5=Numerator5/Denominator;Numerator5=LAcuDomain(0.1)×ADD_(p) ³; LAcuDomain(0.1) is the angularextent (in deg²) of the zone where ACU(α, β)≤0.1 logMAR, inside acircle, CIR, centered on (α, β)=(12,0), which radius is 35 degrees. 12.The method for providing an ophthalmic progressive addition lens asclaimed in claim 7, according to which one calculates the lens so as tofulfil following requirement of a sixth acuity criterion,AcuityCriterion6:AcuityCriterion6≥117.5 D.deg, where:AcuityCriterion6=Numerator6/Denominator;Numerator6=LAcuDomain(0.2)×ADD_(p) ³; LAcuDomain(0.2) is the angularextent (in deg²) of the zone where ACU(α, β)≤0.2 logMAR, inside acircle, CIR, centered on (α, β)=(12,0), which radius is 35 degrees. 13.The method for providing an ophthalmic progressive addition lens asclaimed in claim 7, according to which the method comprises anoptimization routine where at least a target is chosen withinrequirement of an acuity criterion chosen in the list consisting ofAcuityCriterion1, AcuityCriterion2, AcuityCriterion3, AcuityCriterion4,AcuityCriterion5, AcuityCriterion6.